The present disclosure relates to a photographing system and a method for synchronizing image quality thereof, and more particularly, to a photographing system capable of synchronizing image quality between a plurality of cameras and a method for synchronizing the image quality.
Since a color image sensor outputs Bayer image data, an image signal processor (ISP) block for converting the data into an image recognizable by a human eye is required. In typical cameras, such an ISP block may be embedded in a CMOS image sensor, or an integrated chip (IC) separate from an image sensor chip may be mounted on a printed circuit board (PCB), or may be embedded in an embedded application processor or a central processing unit (CPU). A typical ISP block has a function of brightness calculation, white balance (or color tone) calculation and adjustment, noise reduction, contrast adjustment, color conditioning, or the like. In a typical ISP block, brightness and a white balance are required to be adjusted to be suitable for an image for each image scene (frame) so that natural images may be viewed.
Synchronization of image quality may be more important when using a plurality of cameras, which may be used in a stereo camera, an image composition camera (or image registration camera), etc. A stereo camera processes images simultaneously shot by two unit cameras to calculate a distance in an image. Furthermore, since stereo cameras are recently widely used in distance recognition systems of robots, when a robot calculates a distance by using unsynchronized images, the robot may achieve an image-read distance (or calculated distance) which seriously deviates from an actual distance, and this error may cause damage to the robot or may cause the robot to give physical damage. Therefore, for stereo cameras, not only synchronization signals Hsync and Vsync but also brightness and white balance synchronization between unit cameras is important.
Meanwhile, an image composition camera (or image registration camera) simultaneously shoots images by using a plurality of unit cameras, and composes or registers the images. When composing or registering images having different color tones and brightness, a composed or registered image may be unnatural. Therefore, also in this case, not only the synchronization signals Hsync and Vsync but also the brightness and white balance synchronization between unit cameras is important.
The synchronization signals for unit cameras may be output from a CMOS image sensor, or may be output from an ISP block (or chip). Conventional unit cameras have a function of automatically adjusting the brightness and the white balance of an image by using a CMOS image sensor or an ISP block (or chip), and also have a function of enabling a user to manually adjust the brightness and the white balance, but do not have a function of automatically adjusting the brightness and the white balance through interworking between unit cameras.
Furthermore, according to conventional unit cameras, since a CMOS image sensor or an ISP block (or chip) is only able to output the synchronization signals, the synchronization signals cannot be synchronized between the unit cameras. Therefore, in order to synchronize images, a host processor (or host system) is required to store images output from respective unit cameras and perform image processing by using the stored images.
Moreover, in order to adjust the brightness and the white balance of an image between conventional unit cameras, the host processor (or host system) is required to be set so as to automatically adjust the brightness and the white balance of an image of a main camera and manually adjust the brightness and the white balance of an image of a sub camera. That is, the host processor (or host system) is required to synchronize the brightness and the white balance by reading, each time the synchronization is performed, a brightness setting value and a white balance setting value calculated by the main camera and writing the read values in the sub camera.